The investigations underway in our laboratory fall into a few general categories. Our primary research focus is male sexual development and specifically, the mechanisms for the control of the onset of puberty. In our current work, we have developed a primate model, based in part on our previous rat studies. Our recent significant findings include: decreased inhibition of GnRH during puberty; "pubertal brain maturation" advancement in absence of gonadal feedback; occasional large gonadotropin pulses in prepubertal animals; pubertal development association with changes in amplitude not frequency of gonadotropin pulses; increased LH bioassay/LH radioimmunoassay ratio during puberty in castrated male; age-related changes in FSH sensitivity in primate Sertoli cell. We have also used the primate model in our studies on neuroendocrine control of GH secretion. We have extended our clinical studies and demonstrated significant alterations in GH pulsatile secretory patterns in patients with leukemia and GH deficiency. In another clinical observation we have shown significantly increased growth in GH deficient children treated with biosynthetic hGH.